Index: cddl/contrib/opensolaris/cmd/zfs/zfs_main.c
===================================================================
--- cddl/contrib/opensolaris/cmd/zfs/zfs_main.c
+++ cddl/contrib/opensolaris/cmd/zfs/zfs_main.c
@@ -59,6 +59,9 @@
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/fs/zfs.h>
+#ifdef __FreeBSD__
+#include <sys/sysctl.h>
+#endif
 #include <sys/types.h>
 #include <time.h>
 #include <err.h>
@@ -6968,6 +6971,23 @@
 	/* check for legacy mountpoint and complain appropriately */
 	ret = 0;
 	if (strcmp(mountpoint, ZFS_MOUNTPOINT_LEGACY) == 0) {
+#ifdef __FreeBSD__
+		char *default_mount_opts = freebsd_default_mount_options(zhp);
+		if (default_mount_opts != NULL) {
+			const char *tmp = strdup(mntopts);
+
+			if (tmp != NULL) {
+				strlcpy(mntopts, default_mount_opts,
+				    sizeof(mntopts));
+				if (tmp[0] != '\0') {
+					strlcat(mntopts, ",", sizeof(mntopts));
+					strlcat(mntopts, tmp, sizeof(mntopts));
+				}
+			}
+			free(default_mount_opts);
+			free(tmp);
+		}
+#endif /* __FreeBSD__ */
 		if (zmount(dataset, path, flags, MNTTYPE_ZFS,
 		    NULL, 0, mntopts, sizeof (mntopts)) != 0) {
 			(void) fprintf(stderr, gettext("mount failed: %s\n"),
Index: cddl/contrib/opensolaris/lib/libzfs/common/libzfs.h
===================================================================
--- cddl/contrib/opensolaris/lib/libzfs/common/libzfs.h
+++ cddl/contrib/opensolaris/lib/libzfs/common/libzfs.h
@@ -772,6 +772,9 @@
 extern int zfs_mount_at(zfs_handle_t *, const char *, int, const char *);
 extern int zfs_unmount(zfs_handle_t *, const char *, int);
 extern int zfs_unmountall(zfs_handle_t *, int);
+#ifdef __FreeBSD__
+extern char *freebsd_default_mount_options(zfs_handle_t *);
+#endif
 
 /*
  * Share support functions.
Index: cddl/contrib/opensolaris/lib/libzfs/common/libzfs_mount.c
===================================================================
--- cddl/contrib/opensolaris/lib/libzfs/common/libzfs_mount.c
+++ cddl/contrib/opensolaris/lib/libzfs/common/libzfs_mount.c
@@ -80,6 +80,9 @@
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/statvfs.h>
+#ifdef __FreeBSD__
+#include <sys/sysctl.h>
+#endif
 
 #include <libzfs.h>
 
@@ -359,6 +362,38 @@
 	return (zfs_mount_at(zhp, options, flags, mountpoint));
 }
 
+#ifdef __FreeBSD__
+/*
+ * A helper function to look for FreeBSD-specific
+ * mount options, pre-mount.  Right now, this looks
+ * at sysctl vfs.zfs.mount_options.  The results from
+ * this need to be freed by the caller, and should be
+ * prepended to any user-requested mount options (since
+ * a user-requested option may undo one of the system
+ * default options).
+ */
+char *
+freebsd_default_mount_options(zfs_handle_t *zhp)
+{
+	char *retval = NULL;
+	size_t len = 0;
+	int rv;
+
+	rv = sysctlbyname("vfs.zfs.mount_options", NULL, &len, NULL, 0);
+	if (rv == -1)
+		return (NULL);
+
+	retval = malloc(len+1);
+	rv = sysctlbyname("vfs.zfs.mount_options", retval, &len, NULL, 0);
+	if (rv == 0) {
+		retval[len] = 0; /* Ensure NUL end */
+		return (retval);
+	}
+	free(retval);
+	return (NULL);
+}
+#endif /* __FreeBSD__ */
+
 int
 zfs_mount_at(zfs_handle_t *zhp, const char *options, int flags,
     const char *mountpoint)
@@ -366,6 +401,9 @@
 	struct stat buf;
 	char mntopts[MNT_LINE_MAX];
 	libzfs_handle_t *hdl = zhp->zfs_hdl;
+#ifdef __FreeBSD__
+	char *default_mount_opts;
+#endif
 
 	if (options == NULL)
 		mntopts[0] = '\0';
@@ -409,6 +447,20 @@
 	}
 #endif
 
+#ifdef __FreeBSD__
+	default_mount_opts = freebsd_default_mount_options(zhp);
+	if (default_mount_opts != NULL) {
+		const char *tmp = strdup(mntopts);
+
+		if (mntopts[0] != '\0')
+			(void)snprintf(mntopts, sizeof(mntopts), "%s,%s",
+			    default_mount_opts, tmp);
+		else
+			strlcpy(mntopts, default_mount_opts, sizeof(mntopts));
+		free(tmp);
+		free(default_mount_opts);
+	}
+#endif /* __FreeBSD__ */
 	/* perform the mount */
 	if (zmount(zfs_get_name(zhp), mountpoint, flags,
 	    MNTTYPE_ZFS, NULL, 0, mntopts, sizeof (mntopts)) != 0) {
Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
===================================================================
--- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
+++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
@@ -91,6 +91,9 @@
 static int zfs_version_zpl = ZPL_VERSION;
 SYSCTL_INT(_vfs_zfs_version, OID_AUTO, zpl, CTLFLAG_RD, &zfs_version_zpl, 0,
     "ZPL_VERSION");
+static char zfs_mount_options[1024];
+SYSCTL_STRING(_vfs_zfs, OID_AUTO, mount_options, CTLFLAG_RW,
+    zfs_mount_options, sizeof(zfs_mount_options), "System ZFS mount options");
 
 static int zfs_quotactl(vfs_t *vfsp, int cmds, uid_t id, void *arg);
 static int zfs_mount(vfs_t *vfsp);